title: Late reactions to patch test preparations with reduced concentrations of p-phenylenediamine: a multicentre investigation of the German Contact Dermatitis Research Group.
abstract: BACKGROUND
  p-Phenylenediamine (PPD) 1% in petrolatum has been shown in a prospective study to elicit late reactions in 1.5% of routine patch tests, which may be indicative of patch test sensitization.
  
  
  OBJECTIVE
  To assess the frequency of late reactions to reduced PPD patch test concentrations.
  
  
  METHODS
  In 1838 patients, PPD was tested at three concentrations (0.5% pet., group I; 0.4% pet., group II; and 0.35% pet., group III). Patch tests were read on D1 (D2) to D3 (D4); additional late readings were performed on D7, D14, and D21. Patients who were not able to return for all scheduled late readings were telephoned on D7, D14, and D21, and questioned about a reaction at the patch test sites.
  
  
  RESULTS
  Data of 1666 patients (1069 women and 597 men) were eligible. Late reactions were observed in 9 patients, 3 in group I (0.49%) and 5 in group II (0.63%). In 7 of 8 of the patients with late reactions, patch tests were applied for 48 hr. On retesting, 4 of 5 patients became positive at D2 or D3.
  
  
  CONCLUSIONS
  The occurrence of late reactions to PPD may be influenced by patch test concentration and duration. PPD 0.4-0.5% pet. may cause late reactions indicative of active sensitization.
authors.affiliation: Department of Dermatology, University Hospital Essen, University of Duisburg-Essen, Hufelandstrasse 55, Essen, Germany. uwe.hillen@uk-essen.de
authors.forename: Uwe
authors.initials: U
authors.lastname: Hillen
authors.forename: Heinrich
authors.initials: H
authors.lastname: Dickel
authors.forename: Harald
authors.initials: H
authors.lastname: Löffler
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Pfützner
authors.forename: Vera
authors.initials: V
authors.lastname: Mahler
authors.forename: Detlef
authors.initials: D
authors.lastname: Becker
authors.forename: Jochen
authors.initials: J
authors.lastname: Brasch
authors.forename: Margitta
authors.initials: M
authors.lastname: Worm
authors.forename: Thomas
authors.initials: T
authors.lastname: Fuchs
authors.forename: Sven M
authors.initials: SM
authors.lastname: John
authors.forename: Johannes
authors.initials: J
authors.lastname: Geier
mesh_terms: D000328:Adult; D017449:Dermatitis, Allergic Contact / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010328:Patch Tests; D010655:Phenylenediamines / Q000009:adverse effects* / Q000737:chemistry*; D013997:Time Factors; D055815:Young Adult
chemical_list: D010655:Phenylenediamines